The present invention relates to switches of a computer Local Area Network (LAN), and in particular to controlling the data flow to the plurality of switches inside a Logical Switch Set (LSS).
In computer networks, a plurality of end stations can be connected together to form a Local Area Network (LAN). When the number of end stations is small, data can be sent from one end station, to all the other end stations, with each end station only reading data addressed to itself. However, when more and more end stations are connected together, and the amount of data to be transferred between the end stations increases, the amount of time that one station has access to the network decreases. This results in delays in transferring of data from one end station to the other.
Computer network switches, can divide a very large network into a plurality of Local Area Networks. A switch connects one Local Area Network to another Local Area Network, and only transfers data packets from one LAN to another LAN, if that data packet needs to be transferred to the other LAN. In this way, the amount of data packets that are transferred across a network is reduced.
The number of LAN""s in computer networks are steadily increasing, and more and more switches are being used to connect the LAN""s to each other, as well as to connect previously separate computer networks. This is causing computer networks to evolve into tremendous sizes, with many different possible connections between LAN""s and end stations.
Switches are correspondingly transferring a greater number of data packets and the failure of a switch can have large and far ranging consequences. In order to increase the reliability of switches, and to reduce their complexity, Logical Switch Sets (LSS) are formed which are comprised of a plurality of switches. The plurality of switches are grouped together to form the LSS which operates as a single logic packet forwarding device. The grouping together of switches to form an LSS is described in Applicant""s co-pending application having Ser. No. 09/014,548 filled on Jan. 28, 1998, and hereby incorporated by reference. The Logical Switch Set (LSS) is connected to a plurality of outside nodes. These outside nodes can be individual LAN""s, end stations or ports to other switches, depending on the configuration of the overall network. All of the plurality of outside nodes have connections to each of the switches in the LSS.
In order to increase reliability of the LSS as a whole, one of the switches in the LSS is designated as a primary switch, and the other switches are designated as backup or redundant switches. The outside nodes then transfer the data packets to the primary switch and the primary switch then forwards the data packets to the appropriate output. The operating parameters of the redundant switches are kept similar to the operating parameters of the primary switch, and are updated substantially simultaneously with the primary switch. Should the primary switch fail, or links between the outside nodes and the primary switch fail, the outside nodes then transfer data to one of the backup or redundant switches. The chosen redundant switch then becomes the primary switch.
Coordination and control is needed between the outside nodes and the plurality of switches of the LSS, in order to have all the outside nodes properly recognize one of the switches as a primary switch, and to also recognize a failure of a primary switch, and chose a new primary switch.
It is a primary object of the present invention to provide control and coordination between the outside nodes and the individual switches of an LSS to designate one switch as a primary switch, and to recognize another switch as a primary switch, should the original primary switch fail.
The object of the present invention is accomplished by having each of the switches in the LSS, and a management means in the LSS perform diagnostic tests of the link means that connects the switches to the outside nodes and also tests the respective switch. The results of the diagnostic tests are shared among each of the switches and the management means, as well as the outside nodes, by transmitting the results on to a Switch Management Local Area Network (SMLAN). The SMLAN is separate from, and in parallel with, the link means. In particular each outside node has an I/O means and the SMLAN is connected to the I/O means of each node. A judge means of each switch and management means analyzes the results of the diagnostic tests and generates its own selection signal based on the results. The selection signals from each judge means is sent out on a separate selection line, and each judge means is able to read the selection lines of the other judge means. The I/O modules of the outside nodes are also able to read the selection lines. The selection lines are also separate from, and in parallel with, the link means and SMLAN connecting the outside nodes to the LSS.
Failures in any one of the links of the link means, or in one of the switches, can be difficult to detect, especially by just one switch or judge. A communication error, can be caused by the transmitter, the receiver, or the link connecting the two. A transmitter will not be aware of a communication error unless it receives feedback from the receiver. If a transmitter is supposed to receive feedback, does not receive feedback, the problem can be with the transmitter, the link to the receiver, the receiver, and/or the feedback link from the receiver to the transmitter. Therefore several different diagnostic tests need to be performed, and these tests need to be performed at the transmitter and the receiver, which in the case of the present invention involves both the switches and the I/O modules of the outside nodes. Each switch then makes its own determination as to its abilities to perform properly, and generates a corresponding type of selection signal. The I/O mean of each node reads the selection signals from each of the switches and the management means, and determines which of the switches is to be the primary switch. All subsequent data packets are then transferred to the primary switch. Each of the I/O means uses the same rules for determining the primary switch, and therefore all of the outside nodes simultaneously elect the same switch as the primary switch for transferring the data packets.
The management means provides an independent and unbiased determination to allow a majority rules algorithm to be used and thus always obtain a correct result should a single error occur in somewhere in the network. The management means also acts as a type of xe2x80x9ctie-breakerxe2x80x9d should two or more switches be equally qualified to perform as the primary switch.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.